Which is why I think DC would make a good test case. All copies of the regs I've found refer to National Park CCW mirroring the State that the park is located. DC is NOT a State. Same logic behind why DC was chosen for a test case in DC vs Heller. I'm sure that a test case could have been brought in Ill, NJ, or NY, but they are States and it might have been a little tougher.